The present invention relates to a light scanning apparatus that scans a light beam from a light source to form an image, and a scanning type image display apparatus using the same.
Light scanning apparatuses scan a light beam from a light source through reflection and deflection by a scanning device (deflector), and draw an image on a scanned surface. Such light scanning apparatuses often include a light detector that detects the scanned light beam with a light-receiving element. Light detectors include a synchronous detector as a representative one. Besides, the light detectors include a radiation position detector, an amplitude sensor, and the like.
A light beam deflected (scanned) by the scanning device is reflected by a synchronous detecting mirror to be introduced to the synchronous detector. The synchronous detector is constituted by a slit and a light-receiving element. When a spot of the light beam (detection light) reflected by the mirror crosses the slit, the synchronous detector receives by the light-receiving element the detection light which has passed through the slit so as to detect a scanning timing. The adjustment of a light emitting timing of the light source relative to the scanning timing enables aligning of image-drawing start positions.
As the detection light, out of the light beam that is being scanned, used is a light beam proceeding toward a non-effective scan area existing outside an effective scan area (image-forming area) in which an image to be drawn on the scanned surface is formed. This light beam is deflected to the outermost side of a scanned range thereof. Thus, a deflection angle of the detection light is a major factor in determining the maximum deflection angle (amplitude) of the scanning device and the size of the light scanning apparatus.
Light scanning apparatuses miniaturized by characterizing the configuration of a synchronous detecting optical system include the following disclosed apparatuses.
Japanese Patent Laid-Open No. 4-184411 has disclosed a light scanning apparatus miniaturized by devising the disposition of the synchronous detector. More specifically, the light scanning apparatus uses an axial deflector including one mirror surface as the scanning device to dispose the synchronous detector at a position where a light beam deflected by the deflector is directly received, thereby integrating an fθ lens with the deflector.
Japanese Patent Laid-Open No. 9-101472 has disclosed a light scanning apparatus miniaturized by devising a scanning lens. More specifically, a marginal portion of the scanning lens, through which a light beam proceeding toward outside the effective scan area passes, is formed with a detection-light deflecting portion having a refractive index discontinuous to that of a portion through which the light beam proceeding toward the effective scan area passes. The detection light deflected outwardly of the scanning lens by the detection-light deflecting portion is received by a synchronous-detecting-light-receiving sensor provided after the detection-light deflecting portion. Thereby, a scanning position of a main scanning direction is detected.
Japanese Patent Laid-Open No. 2005-164997 has disclosed a light scanning apparatus in which a synchronous detecting mirror is disposed in the vicinity of the scanning device. Between the scanning device and a light separating means, the synchronous detecting mirror that folds part of an optical path therebetween is provided, and a plurality of light beams along the folded optical path are received by a synchronous sensor to perform synchronous detection.
However, in the light scanning apparatus disclosed in the Japanese Patent Laid-Open No. 4-184411, the maximum deflection angle of the deflector needs to be set larger than the normal case, which deteriorates scanning efficiency. The reason for this is that, to provide the synchronous detector in the vicinity of the deflector, the light beam used for the synchronous detection needs to be separated from the light beam proceeding toward the effective scan area on the scanned surface by at least the size of the synchronous detector. As a result, the non-effective scan area is expanded, and thus a ratio of the effective scan area decreases. That is, the scanning efficiency decreases, and the illuminance of an image surface also decreases.
In the light scanning apparatus disclosed in Japanese Patent Laid-Open No. 9-101472, the marginal portion of the scanning lens is used to further outwardly deflect the detection light. Thus, the synchronous detecting sensor is disposed in a position outwardly separated from the scanning lens. This makes it difficult to sufficiently reduce the size of the light scanning apparatus.
The light scanning apparatus disclosed in Japanese Patent Laid-Open No. 2005-164997 uses the synchronous detecting mirror that folds the optical path of the detection light from the scanning device. However, the folding mirror is provided in a light proceeding direction at a position where the entire width of the light beam as the detection light does not overlap the optical path of the light beam proceeding toward the effective scan area. This necessitates an increase of the maximum deflection angle of the scanning device. As a result, similar to the apparatus disclosed in the Japanese Patent Laid-Open No. 4-184411, there occurs a problem in that the scanning efficiency decreases, for example.